Research¶

Voltmeter (Voltage Sensor)¶

• Purpose:

  • Scales a 20kV source down to a 0V-5V range for the Arduino

• Why:

  • Safety: Prevents lethal voltage from reaching the user or the microcontroller
  • Data Integrity: High resistance (20MegOhms) ensures the probe doesn't draw enough current to drop the very voltage you are trying to measure

• Lacked:

  • Voltage Stress Distribution: Documentation lacks a plan for physical spacing between resistors to prevent "surface tracking" (electricity jumping acrosss the board) at 20kV

Beam Modulation / PWM (Digital Pin D9)¶

• Purpose: Controls electron beam intensity or pulse frequency using a MOSFET.
• Why:
  • Granular Control: Provides a way to dim or brighten the beam rather than just having it fully on or off.
  • MOSFET Protection: The 100ohms gate resistor is critical to stop electrical ringing that occurs during high-speed switching
• Lacked:
  • Thermal Calculation: Documentation doesn't specify the maximum Duty Cycle allowed before the MOSFET requires an external heatsink to prevent melting

Beam Enable (Digital Pin D8)¶

• Purpose:

  • Provides a master hardware enable/disable for the beam

• Why:

  • Predictability: The 10kohms pull-down ensures the beam cannot fire during the few seconds it takes for the Arduino to boot up or if a wire gets pulled out

• Lacked:

  • Redundancy: It lacks a physical emergency E-Stop button that can cut power even if the software crashes

Thermistor¶

• Purpose:

  • Monitors the specific temperature of high-heat components, like the MOSFETs, using a voltage divider and the Steinhart-Hart model

• Why:

  • Direct Thermal Monitoring: Since it’s a physical resistor, it can be mounted directly to a heatsink to detect thermal runaway in your beam control circuits.

  • High Speed: Analog readings are nearly instantaneous, allowing the Arduino to kill power the moment a component overshoots a safety limit

• Lacked:

  • Self-Heating Correction: The documentation doesn't account for the fact that current running through the thermistor itself can raise its temperature, leading to slightly inflated readings

DHT11 Sensor (Digital Data Pin)¶

• Purpose:

  • Measures the ambient air temperature and humidity of the entire environment

• Why:

  • Arcing Prevention: High humidity increases the conductivity of air. Since you are working with 20kV, monitoring ambient moisture is a critical safety requirement to prevent unintended arcing

  • Digital Accuracy: Unlike the thermistor, this sensor sends a pre-calibrated digital signal, reducing the risk of analog noise interference from the high-voltage lines

• Lacked:

  • Slow Sampling Rate: DHT11 sensors typically only update once every 1–2 seconds. The documentation doesn't mention that this sensor is too slow to use for emergency instant shutdowns compared to the thermistor

Status LED (Digital Pin D13)¶

• Purpose:

  • Provides a visual heartbeat indicator.

• Why:

  • Remote Safety: Allows you to confirm the system is alive and running code from a safe distance before you approach the high-voltage hardware.

• Lacked:

  • Fault Messaging: Currently only shows Power On; it lacks the ability to blink specific patterns to tell you which sensor (Temperature vs. Voltage) triggered a shutdown.

9V Logic Level Converter (Voltage Divider)¶

• Purpose:

  • Steps down a 9V power source to a ~3.27V reference using a series combination of 10kΩ, 4.7kΩ, and 1kΩ resistors.

• Why:

  • Component Safety: Provides a safe voltage level that will not overload or destroy 3.3V-rated logic pins or sensors.
  • Accessibility: Utilizes standard resistor values readily available in the ADALP2000 analog parts kit, providing a quick solution without needing specialized ICs for simple reference scaling.

Future Recommendation¶

• High-Voltage Safety

  • Research how much physical space is needed between parts on a circuit board to prevent electricity from "jumping" across the surface at 20kV
  • Look into using special glues or coatings (conformal coating) to cover the high-voltage resistors to stop sparks and protect the circuit from moisture

• Heat Management

  • Calculate exactly how "hard" you can run the MOSFET (the switch) before it gets too hot and melts
  • Research adding a heatsink (a metal cooling fin) or a fan if the switch stays on for long periods, which will keep the components from burning out

• Steady Power

  • Test if the 3.27V output drops or "sags" when you actually plug something into it, which happens because a simple resistor divider isn't meant to provide power
  • Research replacing the resistors with a dedicated voltage regulator chip (like the ADP3300) that keeps the power steady even when the battery gets low or the load changes

• Long-Term Reliability

  • Study how repeated heating and cooling affects the life of your hardware so you can predict when a part might fail before it actually does
  • Since you have a humidity sensor (DHT11), investigate if high humidity makes the high-voltage sections more likely to spark or leak electricity